Behind this listener I want to cach the VE editor part Property sheet page to use it.

I could launch the plugin within the eclipse platform as an eclipse Application. My view is added to the workbench.
The problem appears during the interaction with the workbench, most exactly when I select the VE editor part where my UI are being designed.
Actually, an error dialog is thrown when I click on the VE Editor Part. It's written the following message: An error has occurred. see log error for more details.
in the error log, I find that it's du to the NoClassDefFoundError error java 70.
is this error caused by non configured target environment, spacially the classpath of this last??? I have tried to do it but my afforts were -and still are- fruitless.